1. Field of the Invention
Devices for applying colored markings to cables.
2. Prior Art
The subject of this invention is useful in a system disclosed in U.S. Pat. No. 3,638,612 assigned to the assignee of this invention. That invention discloses a device for marking a longitudinally advancing conductor or cable, which has been freshly extruded with plastic insulation, by a stream of fluid material of a predetermined color. The stream is first ejected from a high pressure nozzle and is sinusoidally deflected by an electrical deflection means. Then the deflection is amplified to be substantially larger than the cross sectional dimension of the cable by an electrical amplifying means before the stream is applied transversely to the cable. Where a complete band mark needs to be made around the cable a second stream may be applied to the cable opposite to the side being marked by the first stream by deflecting amd amplifying the second stream in the same manner as the first stream.
The device described in U.S. Pat. No. 3,638,612 has proved very effective in practice. A stream of color material being ejected from the spray nozzle and deflected by the electric alternating field applied to the electrodes through which the stream passes exerts a force on the more or less chargeable particles distributed in the color material. To achieve an as homogeneous distribution as possible of the more or less electrically charged particles of the color-material/solvent mixture, it is proved to be an advantage to pass the mixture through a large double straining filter before feeding it to the spray nozzles. Because of the presence of very low boiling components of the color-material/solvent mixture there is a distinct possibility that ambient air will be sucked in and there is a risk that the solvent vapors, separating from the mixture on the intake side of the pump, will move as gas bubbles into the spray nozzles. In the spray nozzles this results in a short time interruption of the stream of color material and simultaneously in the particles of the color-material being atomized. Under the influence of the high voltage alternating field these particles reach the deflecting electrodes which produces field distortions. The result is that the distortion of the amplitude of the stream of color material and in the extreme case even an interruption of the same.
Other prior art devices as represented by U.S. Pat. Nos. 3,631,654; 3,650,862; 3,668,822; 3,786,618 and 3,912,468 have been disclosed but do not provide the structure and advantages of the device of this invention.